1. Field of the Invention
This invention relates generally to an electro-optical liquid-crystal display device and more particularly to an electro-optical liquid-crystal display device with two plane polarizers having between them an electro-optical layered structure comprising two parallel, transparent plates provided with electrodes, the plates enclosing a layer of a nematic liquid crystal with wall orientation.
2. Description of the Prior Art:
The operating principle of devices of the type mentioned above is based on the ability to control by means of an electric field the optical activity of a nematic liquid crystal with wall orientation.
Liquid-crystal configurations are known (e.g. DT-OS 2,158,563; DT-OS 2, 202, 555; DT-OS 2, 214, 891; U.S. Pat. No. 3,731,986 ) which exhibit a polarization effect and alter their polarization properties in an electric field. If the electric field is discontinued the substances resume their original polarizing property. A corresponding electro-optical display device comprises in general two parallel, transparent glass plates which are coated on their inner surface with electrodes in accordance with a character to be displayed, and which are surrounded by polarizers. The electrode material can be, for example, a thin, optically transparent coating of an electrically conducting material, such as stannic oxide. Between the two glass plates, which are held at a specified distance from each other by means of a plastic foil, of polytetrafluoroethylene "Teflon") for example, is the layer of nematic liquid crystal, the two glass plates exhibiting wall orientation on their surfaces facing the liquid crystal. The electrodes, or conductors connected to them, include external terminals to allow application of an external voltage. Ambient light passing through the layered structure emerges on the observer's side of the device in the form of plane-polarized light. If a display device of this kind is viewed through a plane-polarizing system, e.g. through polarizing sunglasses, the display contrast perceivable by the eye is dependent on the orientation of the sunglasses relative to the display device. In the most unfavourable case the contrast can disappear completely.